This project consists of three studies. Two cross-sectional studies will be used to test alternative models of[unreadable] the underlying dimensions of individual differences in vocabulary and in fluency, respectively. The goal of[unreadable] study one is to examine two potential dimensions of vocabulary knowledge. The first is a distinction between[unreadable] producing a definition and using a word in context. The second is a contrast between vocabulary knowledge[unreadable] and morphological awareness. The goal of study two is to understand what roles accuracy and rate play in[unreadable] both reading and rapid naming. This study will examine the relation between reading rate and accuracy, as[unreadable] well as between rapid naming rate and rapid naming accuracy, using a confirmatory factor analysis with[unreadable] multiple measurements of the constructs to create latent variables. This study will address the extent to[unreadable] which individual differences in accuracy and rate when reading passages for comprehension are indicators[unreadable] of (a) the identical construct of reading skill, (b) distinct yet correlated constructs, (c) independent constructs,[unreadable] or (d) negatively correlated constructs because of speed-accuracy tradeoffs. The study also will address[unreadable] these same four possibilities for speed and accuracy in the rapid naming task. In addition, the study will[unreadable] address the relation between speed and accuracy measured in the context of reading passages for[unreadable] comprehension and in the context of rapid naming tasks. Participants in the first two studies will be 100[unreadable] second-grade and 100 fourth-grade children respectively. Participants in a follow-up longitudinal study will[unreadable] be 300 first-grade students who will be assessed annually through fourth grade. This study will serve to test[unreadable] alternative models of developing causal relations among nine key constructs: phonological awareness,[unreadable] decoding, vocabulary-including morphological aspects, fluency, reading comprehension, spelling, written[unreadable] expression, working memory, and listening comprehension.